Effect of Length on the Performance of Lean NO_x Traps

Author

Vitaly Y. Prikhodko, University of Tennessee - Knoxville

Date of Award

8-2007

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Ke Nguyen

Committee Members

Stuart Daw, J. Roger Parsons, David K. Irick

Abstract

The effect of monolith length on the NO_x performance of two different Lean NO_x Traps has been investigated using a bench flow reactor (BFR). The washcoat composition of one of the catalysts consists of Pt/K/γ-Al₂O₃; the major components of the other catalyst include Pt, Pd, Rh, barium, ceria and zirconia supported on γ-alumina washcoat. Samples of 2.22-cm in diameter and length of 2.54, 5.08 and 7.62-cm within each LNT were evaluated with long and short-cycle experiments at a fixed gas hourly space velocity, and results were compared between samples of different lengths. No significant difference in performance was observed in long and short-cycle experiments with full regeneration. On a contrary, significant difference was observed in short-cycle experiments with partial regeneration: the longer the sample the better the performance.

The intra-catalyst concentration of H₂ measured at different axial locations in short-cycle experiments indicated higher H₂ consumption in shorter samples. A series of experiments was carried out to ascertain different mechanisms of H₂ consumption, and results indicated different degrees of lean and rich front back-mixing for samples of different sizes. Higher back-mixing in shorter samples resulted in a higher H₂ loss via its oxidation by O₂ and lesser H₂ availability for reducing stored NO_x, which in turn affected catalyst’s performance when regeneration was limited by amount of H₂ available.

Recommended Citation

Prikhodko, Vitaly Y., "Effect of Length on the Performance of Lean NO_x Traps. " Master's Thesis, University of Tennessee, 2007.
https://trace.tennessee.edu/utk_gradthes/193